ES2276838T3 - ACCESSORY DRIVING SYSTEM INCLUDING A MOTOR / GENERATOR. - Google Patents

Abstract

The invention is an improved belt drive system for a power plant. It is of the type having a crankshaft pulley, an accessory pulley, a motor/generator pulley, a belt tensioner, and a belt tensioner pulley. It also includes a power transmission belt trained about the crankshaft, accessory, motor/generator, and the belt tensioner pulleys. The power transmission belt has spans defined by terminations proximate to each of the pulleys, including intermediate spans beginning at the crankshaft pulley and ending at the motor/generator pulley following the direction of belt travel in normal operation. The first of the intermediate spans has a first termination end proximate the crankshaft pulley. The last of the intermediate spans has a last termination end proximate the motor/generator pulley. It is improved by the tensioner pulley being proximate a termination end of an intermediate span not being either the first termination end or the last termination end.

Description

Accessory drive system that It includes a motor / generator.

Background of the invention Field of the Invention

This invention relates generally to systems. Transmission or belt drive of motor accessories of internal combustion, whose systems include each of them a unitary device that performs both the commissioning function motor running as the function of electric power generation,  such as an engine / generator, sometimes referred to as a Gen-Star More particularly, the invention is refers to such application systems in cars. Specifically, this invention relates to a configuration for belt drive systems each of which has a motor / generator and each of which has a tensioner.

Description of the state of the art

Internal combustion engines use normally drive belt drive systems of power to take power from the engine crankshaft and supply it to one or more different auxiliary or motor accessories. In applications in cars, such accessories include pumps steering mechanics, water pumps, air compressors conditioning, fuel pumps and alternators. Historically, these engines have used, as the main point of making power, the crankshaft protruding from the rear of the engine to which the transmission train is coupled to drive the wheels and thus cause the movement of the car. The accessories are driven by a pulley attached to the front of the crankshaft. Each accessory is equipped with a pulley. All accessories are in mechanical communication via one or more belts power transmission dragged around them. This provided some tensioning method of each of the belts of power transmission. The power transmission belt, the pulleys and the devices that carry out the tensioning of the belts constitute the belt drive system of the accessories.

The first systems included multiple V-belts Normally, each of the straps was tensioned by manual adjustment and fixation of the position of at least one of accessories or crazy pulley by belt. These systems are known as center-locked belt drives, due to that there is no provision for automatic movement of any of the pulleys to adapt to a variable condition of a belt or drive as a whole. In the event that the belt should stretch or extend in any other way, the tension on the belt should then be less. Also, for a proper operation of the belt drive system, the belt tension must be set sufficiently high to adapt to the worst case conditions. These worst case conditions may be the result of extreme situations of temperature, engine operation or Accessory operation.

There has been interest in making the volume of car engine compartments be smaller. To adapt to smaller compartments, several aspects of the engines have become smaller, including those belt drive systems of accessories. This has been carried out, at least in part, reducing the number of employees straps. As each belt is removed and thereby reduced the number of layers that extend from the front of the engine, the total distance over which the belt drive system from the front of the engine. Finally, this has resulted in the use of only one serpentine strap for many applications. The strap on serpentine receives such a name due to the way in which it drag around the various pulleys in a series of curves, both forward and backward. For applications in serpentine, a V-belt is very suitable Ribbed or Micro-V (a registered trademark of The Gates Rubber Company).

The limitations of the center's approach locked in the belt tensioning are exacerbated in the case of Serpentine applications. Therefore, most of the Modern serpentine belt drives include a tensioner automatic by which you can better absorb the changing conditions of the belt drive system. In its basic form, an automatic tensioner includes a structure that directly or indirectly coupled to the engine cylinder block, and a pulley that applies pressure on the belt in the plane of rotation of the belt drive system. A moving element it extends between the structure and the pulley and is requested to provide pressure on the belt, by means of the pulley. The pressure acts to prolong the distance around which it is dragged the belt, thereby causing the tension of the belt. Be they have used various techniques and geometries to provide the solicitation force Normally, a resilient element, such Like a steel spring, it acts to force the moving element  make a linear or rotational movement, which makes the tent pulley to move in one direction towards a surface of the belt, which, in turn, tends to increase tension on the belt.

A tensioner with only these elements provides a somewhat constant force on the belt surface when the system is in a state of rest (i.e. pulleys they are not spinning). The dimensional instability of the system drive caused by time, temperature or variables in manufacturing is absorbed relatively well through the action of the resilient element, at least within the limits of linearity of the resilient element and tensioner geometry. Of this mode, the tension on the belt remains relatively constant, when the system is stopped, even if the belt may have been stretched or the engine may be hot or cold. But nevertheless, a tensioner with only these elements may not maintain tension suitable on the belt in all operating conditions of the system.

A belt drive system in operation usually oscillates due to the influences of the torsional vibration or other angular acceleration of the crankshaft or accessories, to the influences of unbalanced conditions or to Other influences Torsional crankshaft vibration occurs, in part, as a result of the different impulses supplied to the crankshaft through the combustion cycles of each combination of cylinder and piston. The oscillations lead to the vibration of the belt. This, in turn, leads to the vibration of the parts tensor mobiles. An amount of movement then accumulates in said moving parts, modifying the force that the pulley exerts on the belt surface and tension on the belt. He change of tension on the belt may cause behavior unacceptable belt drive system. In a case, short-term behavior problems may arise, such as when the belt belt drive system belt excessively limiting the efficiency or transmission capacity of system power, or it is excessively noisy due to that the belt slips or due to other reasons. In another case, the amount of tension necessarily applied to the belt, so that your behavior is acceptable in the short term, leads to problems to long term such as premature failure of one or more components of the system, including the strap, or one or more accessories.

To solve these problems and improve the tensioners behavior, they have been included in them damping devices The first buffered tensioners they included symmetric damping where the movement of the moving parts of the tensioners is damped in a way approximately the same regardless of the movement instantaneously occurs in the direction tending to increase the tension on the belt or in the direction tending to decrease the belt tension. The damping is combined with the forces supplied by the resilient element to give rise to a modified request at the pulley / belt interface. Others Tensioners have used asymmetric damping. Usually, said tensioners are damped so that the damping over the moving part is minimal when the tensioner is moving in the tensioning direction of the belt and maximum when moving in the direction of loosening the belt.

Certain approaches to asymmetric damping have been passive in nature. The mere direction of movement of the moving parts creates the different degrees of damping. In one such approach, a shoe is requested against a track at a different angle than normal to the surface of the track. As a result, the relative movement of the shoe and track in one direction tends to lift the track shoe. This reduces the pressure at its interface, reduces the friction that results in the damping and thereby reduces the damping. The other direction tends for the shoe to wedge against the track and increase the damping, as shown in Figure 2. According to another approach, described in US Patent of Meckstroth et al . No. 5,439,420, a damping fluid is channeled through different holes through valves that depend on movement with respect to the moving parts of the tensioner. When the tensioner moves in the tensioning direction, the fluid passes through a relatively large hole or channel that offers little resistance to fluid movement and little damping. In the loosening direction, the fluid passes through a relatively small hole or channel that offers a larger resistance and also a larger damping.

Another approach has also been implemented with respect to asymmetric tensioning of the tensioner, as described in the '420 patent. In the `420 patent two are exposed asymmetric active modalities. In one of them, a solenoid Electric deploys brake shoes. When the shoes, the movement of the tensioner is damped in both addresses. In addition, a wedge cooperates with the shoes to modify  the force with which they unfold when the tensor. The damping increases when the tensioner moves in the direction of loosening and descends when the tensioner moves in the tensioning direction. In the other mode, a solenoid displays a piston, which modifies a fluid path and with it Modify the damping. Another approach to the tensioner, described in the `420 patent, it consists in using a solenoid, similar to the two tensioners damped asymmetrically active, and includes a blocking factor to switch the tensioner between two operating modes. In one of the modes, the tensioner works As an automatic tensioner. In the other way, your moving parts are blocked causing the tensioner to act largely on it way that a center tensioner locked.

The `420 patent is aimed at solving the unacceptable behavior of a drive system by belt created by inertial forces caused by the masses rotary of the accessories and crazy pulleys when they decelerate quickly. As described there, when a sudden rotational deceleration in the engine crankshaft "the high rotational inertia of the alternator makes it remain turning and causes the alternator to pull the tensioner in one direction in order to loosen the belt [of the configuration of specific drive shown] ... as a result of the drive belt (sic) patina ... ".

Traditionally, an engine of electric starter to rotate the engine crankshaft so that Combustion can begin and the engine starts running. He starter motor is located near the back of the motor and is adapted to intermittently engage with the Rear of the crankshaft through a gear train.

Normally, there is an increase in pressure to reduce emissions and increase fuel economy by decreasing the weight of the car and reducing the number of components that are under the hood. A proposed approach to these objectives involves the combination of the function of the starter motor and the function of the alternator into a single device, a motor / generator or a Gen-Star. Likewise, with the aim of increasing fuel economy, the Gen-Star promotes the use of a feature that is called "stop-in-neutral." This feature is to let the engine stop when it should normally run in neutral, after which it starts again when it is considered that the car should resume its movement. This characteristic or measure substantially increases the demands on the belt drives of accessories. In practice, the engine / generator is placed in mechanical communication with the crankshaft via the belt drive of the accessories. The motor / generator and the associated belt drive system of the accessories tend to be located on the front of the engine. However, it is contemplated to be able to place these systems in other places, including the back of the
engine.

The emergence of the systems Gen-Star makes the designer of the systems drive belt drive power have to face new and important challenges. An important challenge, between these, has been the development of a tensor system that gives rise to a acceptable behavior, by a belt drive Accessories included in this new device, which not only offers a substantial rotational load and inertia, but also adds a large drive torque in the belt drive of the accessories. In addition, this large drive torque is provided in a flashing mode

DE 198 49 659 showing the characteristics indicated in the preamble of claim 1, describes a tensioning device for belt drive. He tensioning device comprises a unit tensioner-damper, a first tension element in contact with the tensile element and a second element of tension in contact with the traction element. Unit tensioner-damper acts between a first pivot lever and a second pivot lever. The first tension element is connected to the first lever of pivot, which pivots around a first pivot axis permanent. The first tension element is requested by the first pivot lever, under the action of the tensioning force of the tension-damping unit, against a first section of the belt. The second voltage element is connected to the second pivot lever The second pivot lever pivots around a second fixed pivot axis. The second tension element is requested by the second lever of pivot, under the action of the tensile force of the unit tensioner-damping, against a second section of the belt. A belt deflector pulley is disposed between the First section and the second section. Each of the first and second levers is formed by an inner lever that starts from its point of support and by an external lever arm that starts from its point of support, being connected the free end of each arm of external lever to the associated tension element and being articulated the free end of each inner lever arm to one of the ends of the tensioner-damping unit. The tensioner-damping unit is provided with floating form between the inner lever arms and transmits the reaction forces that occur during the operation of tensioned between the first section and the second section. The length of the inner lever arm and outer lever arm of the First pivot lever and lever arm length inside and outside lever arm of the second lever pivot form a relationship that is adapted to the forces of uneven traction in the two sections, so that the length of the inner lever arm and that of the outer lever arm of the first pivot lever form a relationship that produces a pre-tensioning force on the first section, whose pre-tensioning force is of different magnitude regarding the pre-tensioning force produced by the second pivot lever on the second section.

A different tensioning system, established as an approach to tensioning a belt drive accessories that incorporates a motor / generator, described in the Japanese application publication number JP1997000359071. In said publication describes the placement of an automatic tensioner against the section of the belt that will become the loosest section at the moment when the motor / generator is in the mode starter, except for the presence of the tensioner. This section corresponds to the section that receives the belt immediately after pass the belt through the motor / generator pulley, when the belt It is moving in its direction of normal operation.

The tensioning system described has been identified as less than optimal. To get a acceptable behavior in the short term, the long-term behavior and the width of the belt to be be used to achieve adequate short-term behavior It must be different from the optimum.

Consequently, the need still exists to have a tensioning system that provides the same time, adequate behavior in the short term, behavior adequate in the long term, that optimizes the width of the belt that you can use for any given application that reduces the cost and complexity

Summary of the Invention

The subject matter of the present invention it consists of the provision of a belt drive system of accessories with a configuration that improves the combination of short-term behavior and long-term behavior and that Optimize belt selection.

Another object of the present invention consists in provide an asymmetric tensioner in combination with a configuration that further optimizes short behavior term, long-term behavior and belt width.

To get the above and other objects of in accordance with the purpose of the present invention, as incorporates and describes here extensively, a system is described here of accessory drive that includes such a motor / generator as defined by the features of claim 1. The invention consists of a belt drive system improved for a power generating installation. Said system It is the type that has a crankshaft pulley, a pulley accessories, a motor / generator pulley, a belt tensioner and a belt tensioner pulley. It also includes a strap power transmission dragged around the pulleys of the crankshaft, accessories, engine / generator and belt tensioner. The Power transmission belt has sections defined by endings near each of the pulleys, including sections intermediate starting at the crankshaft pulley and ending at the motor / generator pulley following the direction of travel of the belt during normal operation. The first of intermediate sections has a first termination end close to the crankshaft pulley. The last of the intermediate sections has a last termination end near the pulley motor / generator The improvement is obtained by placing the tension pulley next to the end of a section intermediate which is not the first termination end nor the last termination end

Brief description of the drawings

The attached drawings, which are incorporated into and they are part of the description and in which similar numbers they also represent similar parts, illustrate modalities preferred of the present invention and, together with the description, they serve to explain the principles of the invention. In the drawings:

Figure 1 shows a representation schematic of a preferred mode of a configuration of accessory belt drive system that includes a motor / generator

Figure 2 is a detail of a tensioner that forms part of a preferred belt drive system of Accessories that includes a motor / generator.

Figure 3 shows a representation schematic of a preferred alternative embodiment of a configuration of accessory belt drive system which includes a motor / generator.

Figure 4 is a detail of a tensioner alternative that is part of a preferred alternative system of accessory belt drive and that includes a motor / generator

Figure 5 is a detail of a tensioner alternative that is part of a preferred alternative system of accessory belt drive and that includes a motor / generator

Figure 6 is a block diagram of a path of a control signal.

Figure 7 shows a representation schematic of a preferred alternative embodiment of a configuration of accessory belt drive system which includes a motor / generator.

Detailed description of the preferred modalities

A modality is shown in figure 1 preferred of an accessory belt drive system 10. This system includes a motor / generator 12, a pulley 14 of the motor / generator, a crazy pulley 16, a pulley 18 of a pump steering mechanics, a pulley 20 of an air compressor conditioning, a pulley 22 of a water pump, a pulley 24 of the crankshaft, a tensioner 26, a tensioner pulley 28 and a belt power transmission 30. The transmission belt portion of power 30 that would otherwise hide tensor 26, has been sectioned

Although pulleys for accessories are illustrated specific in a geometric arrangement also specific, must it is recognized that the present invention can be applied to several numbers and combinations of accessories and geometric arrangements, including both serpentine and non-configurations serpentine, depending on the application contemplated. The Illustrated configuration is in serpentine. In this way, the belt Power transmission 30 will normally be of the belt type ribbed trapezoidal. However, the invention can be put into practice with the inclusion of all types of belts. In addition, this Figure can also be appreciated as a belt / pulley plane in an accessory belt drive system that has Multiple straps

The arrow marked "route of the belt "indicates the direction of travel of the belt during the Normal operation in both generation and start modes. For its movement downstream, along the route laid by the power transmission belt 30, has to move in it direction that the belt travel. To move upstream has to move in the opposite direction of the path of the belt.

For the downstream movement that starts in the crankshaft pulley 24, a first intermediate section 32 covers the distance that begins with a termination at the last point of contact between the crankshaft pulley 24 and the drive belt of power 30, and ending with a termination in the first point of contact between tension pulley 28 and belt power transmission 30. A final intermediate section 34 covers the distance that begins at the last point of contact between the pulley tensioner 28 and power transmission belt 30 and ending at the first point of contact of the pulley 14 of the motor / generator and the power transmission belt 30. In the event that add pulleys, which come in contact with the first section well intermediate 32 or with the last intermediate section 34, they would get additional intermediate tranches. On the other hand, the stretch boot-strike-side 36 covers the distance from the point of contact with the pulley 14 of the motor / generator to the point of contact with the idler pulley 16.

The torque direction on pulley 14 of engine / generator and in the pulley 24 the crankshaft is invested in function of the operating mode of the drive system belt 10 of the accessories, as indicated by the arrows marked with "boot" and "generation", in each of the pulleys 14 and 24, respectively. In the generation mode, the pulley 24 of the crankshaft supplies the entire drive torque. The Water pump pulley 22, air compressor pulley 20 conditioning, pulley 18 of the steering pump and pulley 14 of the motor / generator consume the driving torque, with a consumption minor by the idler pulley 16 and tension pulley 28. In the mode starter, the pulley 14 of the motor / generator supplies all  of the driving torque. The crankshaft pulley 24, the pulley 22 of the water pump, the air conditioning compressor pulley 20 and the pulley 18 of the steering pump consumes in torque of drive, with lower consumption by the idler pulley 16 and tension pulley 28.

In general and regardless of the mode of operation, in the event that it is assumed that each of the pulleys are allowed to turn freely, the tension on each of the sections would be the same and it would be static tension. The tension static is the result of the force coupled to the belt power transmission 30 by tensioner 26 by means of pulley 28 of the tensioner that tends to extend the distance at which the belt Power transmission 30 is forced to travel around All the pulleys. However, when the pair is supplied and consumed by the various pulleys of the drive system by belt 10 of the accessories, such as when the system belt drive 10 of the accessories is working, it Modify the tension in each of the sections.

In the conventional or generation mode, the crankshaft pulley 24 and the section of lateral-tensioning generation 38 supply the driving torque and constitutes the section with the larger tension, respectively. In each section upstream of the lateral-tension-generation section 38, the tension on the power transmission belt 30 is reduces by the effect of each of the consuming pulleys of the pair immediately preceding the section. Pulley 14 motor / generator has the largest load, in most cases. Consequently, the largest voltage difference, due to to the load, it appears normally when it goes from the section of start-strike-side 36 to last intermediate section 34. In general, the trend continues until point where the first intermediate section 32, with a termination in the pulley 24 of the crankshaft, it presents the lowest tension.

In the conventional drive system of Accessories by ribbed belt, considerations Fundamental in the design are: 1) the width of the belt (normally represented by the number of nerves) and the selection of the type in relation to the pair that must be supplied and consumed; and 2) static voltage selection so that it is below the one that imposes loads well on the belt or on the system components until the point of reducing the lifespan both below a period acceptable as above the point where it begins to occur an unacceptable skating. In addition, the type of belt and the selection of the width affect the service life of the belt. Similarly, there is a combination between these two considerations. fundamental in the design.

A constant goal for the designer of a accessory belt drive system consists of optimize both considerations, in light of concerns of both Cost as complexity. Optimization is achieved through the manipulation of many geometric and material parameters, known to those skilled in the art. Among these is the arrangement of the conductive and driven pulleys based on the pair of inertia or another pair that each one presents.

Drive systems that include a motor / generator have new and difficult limitations and, even Now, they have alluded to practical optimization. The root of such difficulties lies in the fact that the pulleys they supply the drive torque and present the load and inertial torque more large, they are different depending on the mode of operation. In addition, larger inertial torque loads are presented than normally found in a drive system conventional.

In start mode, the engine / generator 12 supplies the drive torque. The last intermediate section 34 It is the stretch with the greatest tension. The first intermediate section 32 it has a tension only slightly reduced by the small load presented by the tensioner pulley 28. Unlike in mode generation, the crankshaft pulley 24 has the most load big. Similarly, the largest voltage difference, such as consequence of the load, is between the first section intermediate 32 and the stretch of lateral-tensioned generation 38. As can be seen, the layout that is optimal in the generation mode is substantially different from the arrangement that is optimal in the boot mode

The arrangement of the preferred mode illustrated greatly optimizes the drive system by belt 10 of accessories in certain applications for combination of modes, particularly when coupled with the tensioner 26 shown in figure 2. Tensioner 26 comprises a pulley 28 of the tensioner, a main pivot 40, a pivot 42 of the shock absorber, one arm 44 of the shock absorber, one shoe 46 of the shock absorber, a track 48 of the shock absorber, a spring of solicitation 50, ratchet teeth 52, a tongue 54, a pivot 56 of the tongue, a firing pin 58, a solenoid 60 and conductors 62. Pulley 28 of tensioner, track 48 of shock absorber, teeth 52 of the ratchet, the request spring 50 and the pivot Main 40 are supported by the tensioner structure 64. He request spring 50, in this mode, is a coil of steel. Other resilient elements, including elastomeric or pneumatic elements.

It will be noted that tensioner 26 is located between the first intermediate section 32 and the last intermediate section 34. In the generation mode, the first intermediate section 32 carries the less tension The last intermediate section 34 carries no tension directly altered by the torque of the pulley 14 of the motor / generator.  The tensioner 26 acts to place the static tension for the entire Accessory belt drive system 10, downstream of the pulley 24 of the crankshaft and upstream of the pulley 14 of the motor / generator The request spring 50 acts to request to pulley 28 of the tensioner. In generation mode, tongue 58 and the ratchet teeth 52 are uncoupled, as is illustrates

When the condition of the belt allows power transmission 30, the request spring 50 causes the distance covered by the request spring 50 is extended. In turn, the tensioner pulley 28 supported by the structure 64 of the tensioner rotates around the main pivot 40 to the right and in the tensioning direction as indicated in figure 2. The spring of request 50 causes the arm 44 of the damper to press the shock absorber shoe 46 against track 48 of the shock absorber. To the same time, the right movement in combination with the geometric relationship of the main pivot with the pivot of the damper causes the track 46 of the damper to move to rights below the shock absorber shoe 46, resulting in a damping friction. Damping friction tends to subtract from the solicitation applied by the tensioner pulley 28 to the power transmission belt 30. However, the movement to rights and the ratio of pivots 40 and 42 tend to decrease the coupling force of the shoe 46 with the track 48. From this mode, the damping friction is lower when the pulley 28 of the Tensioner rotates in the tensioning direction.

When the condition of the drive belt power 30 forces the tensioner pulley 28 to rotate in the loosening direction, by overcoming the force provided by the request spring 50, the movement to the left and the ratio of main pivot and shock absorber 40 and 42 tend to increase the coupling force of the shoe 46 with the lane 48. In this way, the damping friction is increased when tension pulley 28 rotates in the direction of loosening. The damping friction tends to add to the solicitation that the tensioner pulley 28 applied to the power transmission belt 30. Consequently, in the generation mode, the tensioner 26 acts as an asymmetrically damped passive tensioner. This configuration and asymmetric damping provide a substantial benefit towards system optimization belt drive 10 of accessories, when operating in the mode of generation.

When the belt drive system 10 of accessories must operate in boot mode, the sensor mode 66 (figure 6) detects the presence of boot mode. He mode sensor can be an electric switch or separate ruler driven at any time when the motor / generator 12 receives electrical power to activate the drive system by belt 10 of accessories, or it can be part of a ignition switch for cars. The 66 mode sensor is normally found within a controller for the motor / generator The signal that is produced by the mode 66 sensor it is passed to signal processor 68, which may consist of a variety of electrical circuits to process the signal and make it compatible with actuator 70. The elements of this travel of the signal and associated components, the mode 66 sensor, the signal processor 68 and actuator 70 are already known to the subject matter experts. The actuator 70, in this mode preferred, comprises a solenoid 60 having a piston 58 and conductors 62. While this preferred mode contemplates the use of electrical signals, sensors, processors and actuators, the use of mechanical, hydraulic and tires, signals, sensors, processors and actuators.

The signal to solenoid 60 is passed via the conductors 62. Solenoid 60 reacts to the signal by raising the piston 58, causing the tongue 58 to rotate around the pivot 56 of the tongue to the point of coupling the tongue 54 with the ratchet teeth 52. When configured in this way, with the blocking factor, the tensioner pulley 28 can act with ratchet in the tensioning direction, but is limited or blocked in its movement in the direction of loosening.

As described above, the last intermediate section 34 becomes the section with the greatest tension when the belt drive system 10 of the accessories It is in boot mode. The pair of pulley 24 Crankshaft does not directly alter the tension on the first section intermediate 32. The section of start-strike-side 36 reaches Be the stretch with the least tension. Without the operation of actuator 70, the tensioner 26 will be forced towards the limits of its travel and will allow the power transmission belt 30 be dragged around the path of the shortest distance possible. The time required for the transmission belt of power 30 to assume this new route will depend on the amount of damping friction supplied by the combination of the cushion shoe 70 and track damping 48. If a configuration of different damping, as set out below, then the time would depend on the level of damping provided by the Applied configuration

However, the coupling of the tongue 54 with teeth 52 retains tensioner 26, which in turn restricts the power transmission belt 30 to travel along the which was dragged just before the drive system per strap 10 of the accessories be placed in boot mode. Consequently, the voltage on the drive system by belt 10 of the accessories does not decrease substantially when Switch the mode. Importantly, this allows the selection of a static tension, via the degree of spring elasticity of request 50 and overall geometry of the tensioner 26, which is significantly lower than allowed by configurations so far available, without short-term behavior suffer improperly.

When the mode is switched, from the mode of start to generation mode, actuator 70 is deactivated, allowing the tongue 54 to disengage from the teeth of ratchet 54, and allowing the tensioner 26 to return to the mode of generation described above.

Activation of actuator 70 may be based strictly on the input from the mode 66 sensor or in additional parameters found in the signal processor 68. For example, a time delay may be constituted in the operation of the signal processor 68 so that the actuator 70 remain active for a set time a Once the 66 mode sensor indicates that the mode has been switched. In addition, an advantage can be achieved in deactivating the trigger 70 after a set period of time regardless of the moment at which the mode 66 sensor It signals a mode switching. On the other hand, the mode sensor 66 can detect the r.p.m., the pressure in the engine manifold, the torque on the crankshaft pulley 24 or the torque on the pulley 14 of the motor / generator, to determine a mode switching.

A preferred alternative modality is the shown in figure 3. This mode is the same as the previous mode with the exception of alternative sensor 126, which includes mounting plate 128, damping module 130, the main pivot 140 and the mobile element 164. The module of Damping 130 is shown in greater detail in Figure 4. The damping module 130 includes a cylinder 132, a piston 134, a bypass tube 136, a magnetic coil 138, a rod of connection 142, a connection pin 144, a body 146 and conductors 162. Cylinder 132 and bypass tube 136 are filled with rheological fluid 133. In this mode, the rheological fluid 133 is magnetoreological in nature.

Tensioner 126 has a resilient element (not illustrated) that provides the degree of elastic solicitation, by both requests the mobile element 164 in the tensioning direction, is say left. The resilient element may include a torsion spring, a convolutive spring or one of several others resilient torque producing elements. In addition, you can include a lever arm actuated by a linear resilient element for produce torque The movement of the mobile element 164 around the main pivot 140 is mechanically communicated to the rod of connection 142. The movement of the connecting rod 142 causes the piston 134 moves inside the cylinder 132, which forces that rheological fluid 133 be transferred from cylinder 132, in one side of the piston 134, to the cylinder 132, on the other side of piston 134, by way of bypass tube 136. This causes the rheological fluid 133 pass through the core of the magnetic coil  138. The activation of magnetic coil 138 via the conductors 162 prints a magnetic field on the fluid magnetoreological 133 and, thereby, increases the viscosity of the fluid magnetoreological 133.

When magnetic coil 138 is not activated, rheological fluid 133 passes through bypass tube 136 of a relatively unrestricted way. Thus, the movement of the sensor 126 is relatively free of damping. However, to as coil 138 becomes activated, the resulting increase  in the viscosity of rheological fluid 133 creates a restriction of rheological fluid flow 133 through the bypass tube 136. There is a direct relationship between the intensity of the applied field on rheological fluid 133 and its resulting viscosity. In function of the size and configuration selected for the tube bypass 136, the damping can be raised to the point of essentially lock the tensioner 126 in place.

The signal path shown in Figure 6 is It also applies to this modality. This mode allows a additional flexibility in how, when and what degree of damping shall apply to tensioner 126. Sensor selection of mode 66 and the manipulation of logic within the processor of signal 68 allows fine tuning of the damping of the tensioner 126. For example, damping can be selected to that is at a very high level, but less than necessary to lock the tensioner 126 in place, immediately after the mode switching of the belt drive system 10 of Accessories to boot mode. Consequently, tensioner 126 will be allowed to respond to the mode change by a slight relaxation in the direction of loosening. Then and after A short period, the damping can be increased to block the tensioner 126 in the new position during the time in which the belt drive system 10 of the accessories se is in boot mode. In addition, the mode 66 sensor may be controlling the activity or position of the tensioner 126. This information can be processed by signal processor 68 to intelligently dampen or block tensioner 126 to adapt to the oscillation or vibration of the drive system by strap 10 of the accessories or to mimic the effect of ratchet of the preferred embodiment described above.

Rheological fluid 133 may also be of electroreological nature In this case, electrostatic plates (not shown) replace magnetic coil 138. The operation and general relations remain the same. In addition, the ratchet arrangement of the first mode described preferred comprising ratchet teeth 52, the tongue 54, piston 58, solenoid 60 and conductors 62, are can be incorporated into the tensioner 126 by fixing the teeth 52 on the mobile element 164 and fixing the remaining parts in a way stationary

Figure 5 shows another modality specific to damping module 130. In this case, hydraulic fluid 156 replaces rheological fluid 133. Consequently, the coil magnetic 138, bypass tube 136 and conductors 162 are missing. In this mode, when tensioner 126 is moving in the tensioning direction, hydraulic fluid 156 is forced from the lower portion of the cylinder 132 into the passage main 154, then going through check ball 148 and going to the upper portion of the cylinder 132. Since the main step 154 is relatively large, the tensioning direction of the operation offers little cushioning. When tensioner 126 is moves in the direction of loosening, the hydraulic fluid 156 is forced from the top of the cylinder 132 into the interior of the minor step 150, inside the lower portion of the passage main 154 and then inside the main portion of the cylinder 132. Minor step 150 is relatively small. Thus presents a substantial damping in the direction of operation of tensioner 126. Control piston 152 is illustrated as substantially retracted. If an actuator is included, similar to that illustrated in figure 2, the control piston 152 can be extend or retract selectively. The description of the operation just exposed assumes that the control piston 152 is fully retracted. If the control piston 152 is fully extended, tensioner 126 can still move in the tensioning direction with minimal damping. But nevertheless, minor step 150 is obstructed causing tensioner 126 to remain locked against its movement in the direction of loosening. This modality enjoys the same flexibility of damping in the direction of loosening than the modality of figure 4.

A modality is also contemplated additional similar to that illustrated in figure 2. The teeth of ratchet 52 and tongue coupling teeth 54 can both are replaced by a straight tooth shape, in as opposed to the shown configuration of sawtooth. The activation then blocks the tensioner 26 both in the direction of tensioned as of loosened. In this case, the ratchet does not reach be available On the other hand, all these teeth can be replaced by the corresponding braking surfaces. This allows great control over the damping that is being offered by the tensioner 26 without bringing the damping to the blocking point

It is also contemplated that certain applications can be adapted with tensioner 26, without damping or active blocking as illustrated in figure 7. Without However, all the modalities illustrated incorporate some form of investment resistance of the management, either damping, blocking or rattling, active or passive, at any time the power transmission belt 30 forces the tensioner 26 or 126 in the  belt loosening direction.

The present invention set forth in the modalities described performs an important optimization of both long-term and short-term behavior while, at the same time, the cost and the cost are substantially minimized complexity.

Claims (8)

1. A drive system by belt for a power unit of the type that has: - a crankshaft pulley (24), - a pulley for accessories (18/20/22), - a motor / generator pulley (14) in mechanical communication with a motor / generator, - a belt tensioner (26), - a belt tensioner pulley (28) and - a power transmission belt (30) dragged around said crankshaft pulley, said pulley for accessories, said motor / generator pulley and said pulley of the belt tensioner, - said transmission belt having power (30) sections defined by endings close to each one of said pulleys, including intermediate sections that begin at said crankshaft pulley (24) and ending in said pulley of the motor / generator (14) following the direction of travel of the belt during normal operation, including - a first section (32) of said sections intermediate that has a first termination end close to said crankshaft pulley (24) and - one last section (34) of said sections intermediate that has a last termination end close to said motor / generator pulley (14), - said tensioner pulley being (28) near an end of termination of an intermediate section that does not it is neither said first termination end nor said last end of termination, - said tensor of the belt (26) asymmetrically by means of a solicitation in a direction tending to cause said transmission belt of power (30) is under tension, - said request being asymmetric - - no greater than that provided by the solicitation in a spring regime, when the external forces acting on said belt tensioner (26) and said tensioner pulley are smaller than necessary for overcome said request in a spring and tenant regime consequence of causing said tensioner pulley to move in a direction that increases the tension in the belt, and - - that which results from said solicitation in spring regime and resistance to management reversal, when said external forces that they act on said tensioner and said tensioner pulley are greater than those necessary to overcome this request in spring and thus tending to cause said tensioner pulley to move in a direction that decreases the tension in the belt, characterized because - said investment resistance of the address is applied intermittently in response to the mode of operation of said motor / generator. 2. A drive system by belt according to claim 1, wherein said pulley of the tensioner (28) is close to a second termination end of said first intermediate section (32) and which is opposite with respect to said first termination end. 3. A drive system by belt according to claim 1, wherein said resistance to the investment is derived from a damping factor that responds to movement of said tensioner (26) in a direction of decrease of belt tension 4. A drive system by belt according to claim 1, wherein said resistance to the Management reversal is derived from a blocking factor that responds to the movement of said tensioner (26) in a direction of belt tension decrease. 5. A drive system by belt according to claim 1, wherein said application Intermittent direction reversal resistance is such that said tensioner (26) is damped at a first level of damping in the direction of decrease of the tension of the belt when said motor / generator is running in a mode of engine and such that said tensioner (26) is damped on a second level damping in the direction in which the tension of the belt when said motor / generator is running in the mode of generator. 6. A drive system by belt according to claim 1, wherein said application of intermittent direction reversal resistance is such that said tensioner (26) is blocked against movement in the direction in which the belt tension drops when said motor / generator is running in engine mode and is such that said tensioner (26) is not blocked against movement in the direction in which the belt tension drops when said Engine / generator is running in generator mode. 7. A drive system by belt according to claim 1, wherein said application of intermittent direction reversal resistance responds to a control input resulting from said mode of operation of the engine / generator. 8. A drive system by belt according to claim 7, wherein said control input It is an electrical impulse.